Concrete is a common and popular composite material used for constructing structures. It is used to make roads, buildings, walls, and floors. Concrete may be composed of water, granular solids, and binders, along with other materials, that are mixed together to form a highly viscous fluid that cures and dries into a hard, rigid mass. When used in flooring applications, i.e. building foundations, a flooring material may be applied onto the concrete surface. Some examples of flooring material are chemical finishes, wood, tile, and flooring covers such as carpet and vinyl.
Adhesives are used in a number of applications for holding, protecting, and sealing purposes. In the flooring industry, adhesives are used to bond flooring materials to rigid substrates, such as concrete. During the early part of the 1990s, the flooring industry moved from solvent-born adhesives to aqueous or water-born formulations. Subsequently, it became evident that the water-born formulations were sensitive to elevated concrete moisture and pH. The current standard industry practice to combat the issue of pH catalyzed moisture degradation is to apply a moisture barrier coating with near zero permeability to the concrete surface in order to negate the effects of alkaline moisture attack and protect installation adhesives from failure. Application of said coating can be expensive, difficult, and time-consuming. In cases where floors are subjected to elevated moisture from maintenance, flooding, or relatively high humidity, the failure of these water-born formulations can lead to extensive and costly repairs. Hence, there is a need for adhesives that exhibit alkaline and waterproof properties in order to mitigate the problems caused by high moisture and alkalinity.
Pressure sensitive adhesives (PSAs) are one type of adhesive that can bond two substrates together by surface contact using pressure applied upon at least one of the substrates. These adhesives require no activation with water, solvent or heat, and firmly adhere to many dissimilar surfaces with minimal pressure. Typical PSAs do not solidify to form a solid material, but remain viscous and permanently tacky. Since these adhesives are not true solids, the strength of pressure sensitive adhesives decreases when the temperature is increased. As shown in FIG. 4, PSAs are typically formulated from natural rubber, synthetic rubbers such as styrene/butadiene copolymers (SBR) and styrene/isoprene/styrene (SIS) block copolymers, polyacrylates such as acrylates and methacrylates, and silicone.
Each PSA material can have its own advantages and disadvantages. Disadvantages of rubber-based adhesives include limited effectiveness when exposed to certain chemicals, UV rays, or high temperatures (over 150° F./66° C.). In addition, they are more susceptible to oxidation and may darken, lose their tack, and become brittle if overexposed. Also, rubber/resin adhesives may turn soft and gummy if plasticizers, used in most polyvinyl chloride films (PVC), migrate into the adhesive. Disadvantages of acrylics usually include poor adhesion to low-energy surfaces, such as polyethylene and polypropylene, as well as lower overall adhesion compared to rubber unless the adhesive is highly engineered. Acrylic adhesives are also sensitive to elevated pH and when exposed readily hydrolyze losing the adhesive properties. Silicone-based adhesives can maintain adhesion over a range of temperatures; however, beyond their ability to adhere to difficult surfaces, their overall adhesive strength is low. Hence, there is a need for improved pressure sensitive adhesives.
The present invention features a novel adhesive material that possess alkaline and waterproof properties in order to mitigate the problems caused by high moisture and alkalinity, as well as exhibiting pressure sensitive properties. In some embodiments, the present invention may be used in flooring applications to provide for a strong, durable and permanent adhesion that allows for facile installation of flooring materials.